1. Field of the Invention
This invention relates in general to electrical submersible pumps for wells, and in particular to a discharge head for use with an electrical submersible pump suspended on coiled tubing within the well.
2. Description of the Prior Art
A conventional electrical submersible pump installation for oil wells supports the downhole pump assembly on production tubing. The production tubing is made up of sections of metal pipe secured together by threaded couplings. The submersible pump assembly includes at least one electrical motor, and at least one centrifugal pump. The pump normally locates above the motor and has a discharge head that secures to the production tubing. The production tubing supports the weight of the pump assembly as it is lowered into the well. The well fluid drawn into the intake of the submersible pump will be pumped through the tubing to the surface.
The electrical submersible pump must be maintained from time to time. This requires a workover rig which can pull the sections of tubing from the well to retrieve the pump, then lower a repaired or replaced pump back into the well. This is time consuming and expensive.
One proposal has been to support the pump on the power cable that extends to the electrical motor. This would eliminate the need for tubing and the need for a workover rig to pull the tubing for pump maintenance. Conventional power cable, however, does not have sufficient strength to support the weight of the pump assembly in the well. Consequently, a special cable must be utilized that has sufficient strength to support the weight of the pump in the well. While some of these units have been installed, the expense of the cable has been too high to make this type of assembly common.
It has also been proposed to support an electrical submersible pump on coiled tubing. Coiled tubing is a continuous metal pipe of smaller diameter than typical production tubing. Coiled tubing will coil onto a large reel and can be unrolled into the well. The coiled tubing would have the strength to support the pump assembly in the well. While it requires a unit to uncoil and coil the tubing, the pulling and running back in procedure should be less time consuming than the process of pulling conventional production tubing from the well with a workover rig. Also, coiled tubing would allow the pump to be installed in a live well through a stripper. While the concept of a coiled tubing suspended pump is feasible, this assembly is not commercially available at this time.